Accuracy and clinical usefulness of scoliosis measurement with magnetic spine mapping--Ortelius.

Objectives: Our objective was to assess the accuracy of radiation-free magnetic method of scoliosis curve measurement (Ortelius 800) and its usefulness in clinical practice, as well as to judge whether it can replace x-rays, which represent currently the golden standard for scoliosis measurement.

Background: Patients with adolescent idiopathic scoliosis have to undergo multiple full-length spinal x-rays. Repeated exposure to ionizing radiation leads to higher incidence of breast cancer, thyroid cancer, and leukemia. One of the radiation-free methods that are candidates for replacing the x-rays is the magnetic measurement of the spine with Ortelius 800.

Methods: Twenty-eight patients with adolescent idiopathic scoliosis were measured with Ortelius. Data from Ortelius were compared with standard spinal x-rays taken the same week.

Results: The average Cobb's angle measured by x-ray was 35.11 degrees. The average absolute difference between Ortelius and x-rays was 6.69 degrees. The difference was statistically significant (p=0.0443). An acceptable difference was measured in subgroup of curves that do not exceed 40 degrees (difference 5, p=0.8915).

Conclusion: Ortelius is most accurate in curves in range of 15-30 degrees of Cobb's angle. In larger curves it is increasingly inaccurate. Most important for clinical practice is the Cobb's angle range over 40 degrees, where the conservative therapy is to be replaced with surgery. Ortelius is not accurate enough in this range and therefore cannot fully substitute full spinal x-rays. It can be used to reduce the number of x-rays in the follow-up of smaller curve angles (Tab. 4, Fig. 8, Ref. 10).